During the manufacture of ozone by corona discharge, a corona is generated for ozone production by applying an electrical current across two metallic electrodes separated by a dielectric insulator and an air gap.
The electrical current will not arc between the electrodes because of the dielectric and the air gap. Instead, an energized corona develops in the interstitial space between the electrodes, which is characterised by a deep blue or violet glow.
Ozone is produced by passing oxygen or air through this electrical field wherein a certain percentage of the oxygen molecules dissociate then recombine as ozone.
In some environments such as in cool storage rooms for fruit and vegetables having ozone generators the corona discharge process can be adversely affected by moisture and cold.
Corona discharge ozone cells generally provide more constant ozone output than do UV ozone producing lamps.
Ozone producing ultra violet lamps can deteriorate quite quickly with ozone output declining quite rapidly and corona discharge cells are preferable and allow manufacturers to better develop protocols for ozone concentrations for various fruits and vegetables treatments, however, their use is dependent upon the development of corona discharge cells that can withstand the cold and moisture when placed in cool storage environments.
When using the corona discharge ozone generators to produce ozone air in cool, moist environments, suitable cold and moisture resistant electronic equipment is required.
The electronic control board, transformer, connections, etc. all need to be suitably designed and insulated so they will function under these conditions.
The corona cell assembly itself, over which air is blown by the generator fan to generate ozone, has to be cold-resistant and moisture-resistant so that it functions effectively under these conditions and continues to produce adequate levels of ozone.
In addition, when an ozone generator is controlled by a timer or ozone monitor, the entire electrical assembly including the generating cell will become cold during the time the machine is switched off.
The cell needs to respond quickly when the generator is turned on and recover to ensure a normal corona is again established to produce ozone.
Cold adds current load and as a unit warms up condensation will occur on the outer electrode and on any exposed parts of the dielectric to add more current load, as well as providing an opportunity for arcing to occur. If arcing occurs, the cell can break down and fail.
Electricity will follow moisture so any droplets of moisture that form on the outer electrode or dielectric may allow arcing to travel from the outer electrode along the dielectric and try to reach the inner electrode or enclosure wall. If this occurs, a short can occur resulting in the cell breaking down.
Moisture can also be carried by the generator fan and possibly get between the inner electrode and the inside face of the dielectric.
When the dielectric tubing from off-the-shelf is used the inside dimension is not always uniform. The inner electrode also may not be perfectly uniform in its diameter. As a result, minute gaps are possible between these two components when the cylindrical dielectric is placed over the inner electrode. This situation can lead to leakage and cell failure.
When an ozone generator that generates ozone from air is installed in a confined space to either treat the air or a product with ozone, any residual ozone will be drawn through the ozone generator causing corrosion to certain generator components, particularly electronic components, resulting in malfunction and short working life.
One option is to totally enclose the electronic power board within the generator to safeguard it from residual ozone. Other electronic components such as power sockets, fuse holders etc. can be coated with a suitable epoxy to protect them from ozone.
Standard fans have limited ozone resistance. Further, ensuring all generator components are corrosion and ozone resistant 10 can be expensive and render the generator unaffordable.
Additionally when a corona discharge ozone generation cell is used to produce medium to high levels of ozone from air undesirable nitrogen by-products can form which can also affect generator components. This can be more apparent when such a generator is installed in a cold storage room where moisture levels can be high.
It is an object of the present invention to provide a corona discharge apparatus for generating ozone in air which will operate efficiently in dry as well as cold and wet environments.
It will be clearly understood that, if a prior art publication is referred to herein, this reference does not constitute an admission that the publication forms part of the common general knowledge in the art in Australia or in any other country.